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Full text of "Text Book Of Mechanical Engineering"

|l                      1166                            Appendix VI.

,sj                            (3) adiabatic expansion of the products frpm B to c.    He also

I]                         intended to dispense with water -cooling, but, on account of his

$!.                      alteration of the cycle, was obliged to cool in a very complete

If                        manner,    His proposal, however, to ignite the mixture by the

compression heat has been successfully effected in practice.

Fig. 1029 shews sections through the engine as built.    The
air pump R, worked from the connecting rod M by the lever N
|f;                       and links PQ, supplies compressed  air through  pipe G to the

reservoir j, from which again the vessels H and K are charged,
H for starting purposes, and K as a reserve.    The pressure in
each vessel is indicated at L.    In the cylinder cover are placed
If                        four different valves, of which w is a needle valve to spray oil into

|                          cylinder by air through pipe E, v a starting valve or air pump inlet

|                          at will, b the main air-admission valve taking through Y for the

compression stroke, and a the exhaust valve delivering through x.
These valves are controlled by levers x u, lifted by cams on the
half-speed shaft s, and the oil to be sprayed is further regulated
by the governor z acting on .its own throttle valve. It is most
important that the oil, being coarse and unclean, should be
mechanically purified by the filters A A, or trie spikying needle
would become clogged. These take from pipe c," and deliver
through B by the action of the oil-pump D, which is worked by
crank and rod.from the half-speed shaft, and thus forces the oil
through a fine pipe to the sprayer;

The charge of air taken into the cylinder on the down-stroke
is compressed on the up-stroke to 500 Ibs. per sq. in,, and a
/ temperature of 1000 F. When the piston is at the top, the spray
is admitted at w, and combustion .takes place during the short
period of the down-stroke, indicated at AB, Fig. 1030. As
* nothing but air is compressed, pre-ignition is impossible, and
as an excess is admitted, the .combustion is much slower than
is usual. The high compression is obtained by the adoption of
a very small clearance, only -^th of the working volume, and the
ignition is independent of extraneous assistance. The heat,
however, is considerable, and must be removed by ample water
jackets, which surround the cylinder, cylinder head, and air
pump.

Starting is simple and certain.   Opening the test cock on the